Novak Djokovic was "not really in the mood to speak" after suffering a jarring early defeat at the Monte Carlo Masters, but insisted he would bounce back.

The 35-year-old world number one was playing his 50th main-draw match at the tournament, but it did not go to plan as he lost 4-6 7-5 6-4 to Italian Lorenzo Musetti on Thursday.

Djokovic's post-match reaction exposed huge frustration, with his first competitive outing in over a month ending at the last-16 stage.

He was forced to miss the Indian Wells and Miami tournaments last month, being denied permission to enter the United States due to his refusal to accept a COVID-19 vaccination.

Hopes he had of a long run on the Monte Carlo clay have been scuppered, but the Serbian has plenty of time to find form in time for the French Open, which begins on May 28.

Defeat marked the first time Djokovic had failed to reach the quarter-finals in a tournament since last year's Monte Carlo event, when he lost his opening match to Alejandro Davidovich Fokina.

The loss to Musetti included an argument with the umpire over a line call, while Djokovic also smashed a racket in frustration at one point.

"The feeling is terrible after playing like this, honestly," Djokovic said. "But congrats to him. He stayed tough in important moments, and that's it.

"You always hope for the good day in the office, but I know I'm not playing so great and he's playing very well, so I knew it was going to be a tough match.

"I don't think it's catastrophic, but my feeling is bad right now because I lost the match. It's not a great day for me, so I'm not really in the mood to speak."

Djokovic is a two-time former winner of the ATP 1000 event but has not reached the semi-final stage since 2015, the year he was last champion.

He continues his clay campaign at a low level tournament next week in Banja Luka, Bosnia and Herzegovina.

Musetti moved on to face fellow Italian Jannik Sinner in the quarter-finals. Victory over Djokovic made Musetti the first Italian man to beat the world number one in Monte Carlo since 1973, when the ATP rankings began.